Fiberglass wet exhaust muffler is typically found in V-drive boats or boats with limited space. 4 in. Mini-Max Inline Muffler | Centek Industries 1050400 Centek Minimax muffler Reduces engine noise in boats with limited space between the engine and the transom Fiberglass construction For use with 4 in. inside diameter marine exhaust hose 4 in. hose inlet & outlet 16.75 length 8.38 in. diameter Ideal for V-drive applications and boats with limited space For above the waterline use only Fair sound rating